In a Moving Picture Experts Group 4 Advanced Video Coding (MPEG-4 AVC) standard (Non-patent Reference 1) established by the MPEG under the ISO/IEC, a method for coding a moving picture of RGB format is provided. Here, a conventional method for coding and decoding RGB data by mapping the RGB data to YUV data (where a G signal is mapped to a Y signal, a B signal is mapped to a U signal, and a R signal is mapped to a V signal) is provided.
However, in the conventional method, the RGB signal is coded and decoded using the same method as the conventional method for coding and decoding YUV data. In the conventional coding of YUV data, the same intra prediction mode is used for coding U data and V data, whereas an intra prediction mode used for coding Y data is different from an intra prediction mode used for coding U data and V data. Therefore, when mapping the YUV data to the RGB data, although the same intra prediction mode is used for R data and B data, an intra prediction mode used for G data is different from the intra prediction mode used for R data and B data.
In the conventional coding of the YUV data, a motion vector for Y data is used for motion compensation for the U data and the V data. Therefore, when mapping the YUV data to the RGB data, a motion vector for G data is used for motion compensation for the R data and the B data.    Non-Patent Reference 1: Draft of Version 4 of H.264/AVC (ITU-T Recommendation H.264 and ISO/IEC 14496-10 (MPEG-4 Part 10) Advanced Video Coding, JVT-N050d1, Jan. 28, 2005)